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# Assertion: When $\,{Q_c} = {K_c}\,$, reaction is at equilibrium.Reason: At equilibrium, $\Delta G\,$ is $\,0\,$.A.Both assertion and reason are True and reason is the correct explanation of assertionB.Both assertion and reason are true but reason is not the correct explanation of assertionC.Assertion is true but reason is falseD.Both assertion and reason are false

Last updated date: 12th Aug 2024
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Hint: When a chemical reaction enters equilibrium, the equilibrium constant of a chemical reaction gives insight into the interaction between the products and reactants. It is important to note that, in terms of various units, there are many different types of equilibrium constants that include relationships between the products and the reactants.

Complete step by step solution:
Let us first learn about equilibrium constant of concentration $\,({K_c}\,)$ and reaction quotient $\,({Q_c})\,$;
The equilibrium concentration constant (referred to as $\,{K_c}\,$) of the chemical reaction at equilibrium can be defined as the ratio between the concentration of the products and the concentration of the reactants, each elevated to their respective stoichiometric values.
The reaction quotient $\,({Q_c})\,$ measures the relative concentrations of products and reactants that are present at a given point in time during a reaction. The reaction quotient helps to work out which way, considering either the pressures or the concentrations of the reactants and the products, a reaction is likely to proceed.
In short, $\,K\,$ is the ratio at equilibrium of the relative quantities of compounds to reactants, while $\,Q\,$ is the ratio at some point of reaction time.
Now, coming to the question;
The reaction is in equilibrium as long as the temperature does not change. There is a relationship between $\,{K_c}\,$and $\,{Q_c}\,$. When $\,{K_c} = {Q_c}\,$ the reaction is said to be in equilibrium which implies that the original concentrations are equilibrium concentrations and there are no more concentration changes in the reaction mixture.
Here, Gibbs free energy( it is the free energy which can be used to do the work) less negative when the reaction approaches equilibrium, and eventually reaches zero. So, in equilibrium $\,\Delta G = 0\,$.
Therefore, both the assertion and the reason are correct, but the reason is not the correct explanation for the assertion.
So, for this question option B is the correct answer.

Note:
The equilibrium can be influenced by variations in concentration, pressure , temperature, inert gases, preferring either forward or backward response, but not the equilibrium constant. The equilibrium constant of the reactions does not change when simultaneous equilibrium reactions have a common product. The product concentrations would be decreased due to the higher concentration of the common product.